Because, \( \Large a + \frac{1}{b} = 1 \)

\( \Large ab + 1 = b \) ...(i)

Also, \( \Large b + \frac{1}{c} = 1 \) => \( \Large b = 1 - \frac{1}{c} \) ...(ii)

From Eqs. (i) and (ii), we get

\( \Large ab + 1 = 1 - \frac{1}{c} \)

=> \( \Large ab = \frac{-1}{c} \) => abc = -1